PHP Static Properties

A static property is shared across every instance of the class — and accessible without one.

Declare & use

class Counter {
    public static int $count = 0;

    public static function bump(): void {
        self::$count++;
    }
}

Counter::bump();
Counter::bump();
Counter::bump();
echo Counter::$count;   // 3

self vs static

Same rules as for static methods — self:: means the declaring class; static:: means the runtime class.

Class constants

For values that never change, prefer constants over static properties:

class Status {
    public const PAID     = 'paid';
    public const PENDING  = 'pending';
    public const REFUNDED = 'refunded';
}

echo Status::PAID;

When static properties are useful

• Caches — memoise an expensive computation across instances.
• Counters — total instances created, total events processed.
• Configuration — class-wide default settings.
• Implementing a strict singleton.

When they hurt

• Hidden global state — tests can't easily reset them.
• Multi-tenant code — one tenant's data leaks into another's request.
• Long-lived processes (Swoole, Octane) — static state survives between requests.

Example

<?php
class Counter {
    public static int $count = 0;
    public static function bump(): void { self::$count++; }
}
Counter::bump(); Counter::bump(); Counter::bump();
echo Counter::$count;

Exercise

Test yourself